The present invention generally relates to semiconductor processing, and in particular to a nozzle for applying an edge bead removal material to the edge of a photoresist material layer disposed on a semiconductor wafer.
In the semiconductor industry, there is a continuing trend toward higher device densities. To achieve these high densities there has been and continues to be efforts toward scaling down device dimensions (e.g., at submicron levels) on semiconductor wafers. In order to accomplish such high device packing density, smaller and smaller features sizes are required. This may include the width and spacing of interconnecting lines, spacing and diameter of contact holes, and the surface geometry such as corners and edges of various features.
The requirement of small features with close spacing between adjacent features requires high resolution photolithographic processes. In general, lithography refers to processes for pattern transfer between various media. It is a technique used for integrated circuit fabrication in which a silicon structure is coated uniformly with a radiation-sensitive film, the resist, and an exposing source (such as optical light, x-rays, or an electron beam) illuminates selected areas of the surface through an intervening master template, the mask, for.a particular pattern. The lithographic coating is generally a radiation-sensitive coating suitable for receiving a projected image of the subject pattern. Once the image is projected, it is indelibly formed in the coating. The projected image may be either a negative or a positive image of the subject pattern. Exposure of the coating through a photomask causes the image area to become either more or less soluble (depending on the coating) in a particular solvent developer. The more soluble areas are removed in the developing process to leave the pattern image in the coating as less soluble polymer.
Due to the extremely fine patterns which are exposed on the photoresist material, thickness uniformity of the photoresist material is a significant factor in achieving desired critical dimensions. The photoresist material should be applied such that a uniform thickness is maintained in order to ensure uniformity and quality of the photoresist material layer. The photoresist material layer thickness typically is in the range of 0.1 to 3.0 microns. Good resist thickness control is highly desired, and typically variances in thickness should be less than xc2x110-20 xc3x85 across the wafer. Very slight variations in the photoresist material thickness may greatly affect the end result after the photoresist material is exposed by radiation and the exposed portions removed.
Application of the resist onto the wafer is typically accomplished by using a spin coater. The spin coater is essentially a vacuum chuck rotated by a motor. The wafer is vacuum held onto the spin chuck. Typically, a nozzle supplies a predetermined amount of resist to a center area of the wafer. The wafer is then accelerated to and rotated at a certain speed, and centrifugal forces exerted on the resist cause the resist to disperse over the whole surface of the wafer. The resist thickness obtained from a spin coating process is dependent on the viscosity of the resist material, spin speed, the temperature of the resist and temperature of the wafer.
After the photoresist is spin coated onto the wafer, a rim or bead of photoresist remains on the edge of the wafer. This rim or bead is removed by applying an edge bead removal solvent by using an edge bead removal (EBR) nozzle, so that loose particles from the rim or bead do not become a source of contamination that can cause wafer defects. Typically, the solvent is either applied at the bottom edge of the wafer, while the wafer is spun causing the solvent to wick around the edge and wash off the photoresist bead or the solvent is applied on the top outside edge of the wafer. However, applying the solvent to the top edge of the wafer has its own inherent problems. One of the problems is that when the solvent spray or jet is shut off, a drop of solvent can remain in a nozzle tip of the nozzle, and may free fall onto the wafer undesirably dissolving useful portions of the photoresist material layer, thus destroying the uniformity of the wafer ultimately causing wafer defects.
In view of the above, an edge bead removal nozzle is needed that ensures that droplets formed at a nozzle tip of the nozzle do not fall onto a photoresist material layer that is being worked upon.
The present invention relates to an edge bead removal system and method that employs a nozzle for applying edge bead removal solvent to an edge bead of a photoresist material layer disposed on a wafer. The edge bead removal solvent can be a developer, a rinse or a cleanser. The nozzle includes a liquid chamber that can be connected to a supply of edge bead removal solvent that the nozzle applies through a nozzle tip. The nozzle also includes an air supply chamber that can be connected to a supply of air. The supply of air is isolated from the liquid supply chamber during application of the edge bead removal solvent to the edge bead formed on the wafer. The supply of air communicates via the air supply chamber to the liquid supply chamber thus removing any droplets of edge bead removal solvent remaining in the nozzle tip after application of the edge bead removal solvent is completed. The supply of air can be either positive or negative or both depending on the specific configuration of the nozzle.
One particular aspect of the invention relates to an edge bead removal system that includes an edge bead removal nozzle and an absorbent material that moves from a rest position, during application of the edge bead removal solvent to the edge bead formed on the wafer, to an absorbing position that removes or catches any droplets of edge bead removal solvent remaining on the nozzle tip after application of the edge bead removal solvent is completed. In another aspect of the invention the nozzle includes a liquid supply chamber with an inner cylindrical surface that is rendered hydrophobic for repelling the solvent from the liquid supply chamber or hydrophilic for holding the solvent in the chamber after application of the solvent is completed. The surface can be rendered hydrophobic or-hydrophilic by either being made of a hydrophobic or hydrophilic material or having a surface that is coated with a hydrophobic or hydrophilic material. For example, a hydrophobic material can be coated on the inner cylindrical surface of the liquid supply chamber near the nozzle tip, while a hydrophilic material can be coated on the remainder of the inner cylindrical surface of the liquid supply chamber, or a hydrophilic material can be coated on the inner cylindrical surface of the liquid supply chamber near the nozzle tip, while a hydrophobic material can be coated on the remainder of the inner cylindrical surface of the liquid supply chamber.
Another aspect of the present invention relates to an edge bead removal system for applying an edge bead removal solvent on an edge bead formed on a wafer by a photoresist material application system. The edge bead removal system is adapted to remove a droplet of edge bead removal solvent from a nozzle tip of an edge bead removal nozzle after the edge bead removal nozzle has completed application of the edge bead removal solvent. The system includes a supply of edge bead removal solvent, a supply of air, and an edge bead removal nozzle with a nozzle tip. The nozzle includes a liquid supply chamber adapted to be in fluid communication with the supply of edge bead removal solvent and an air supply chamber adapted to be in fluid communications with the supply of air. The edge bead removal nozzle has a first state for applying the edge bead removal solvent and a second state for removing the edge bead removal solvent from the nozzle tip. The air supply chamber is in fluid communication with the liquid supply chamber in the second state.
Another aspect of the present invention relates to an edge bead removal system for applying an edge bead removal solvent on an edge bead formed on a wafer by a photoresist material application system. The edge bead removal system is adapted to receive a droplet of edge bead removal solvent from a nozzle tip of an edge bead removal nozzle after the edge bead removal nozzle has completed application of the edge bead removal solvent. The system includes a supply of edge bead removal solvent, an edge bead removal nozzle with a nozzle tip. The nozzle is in fluid communication with the supply of edge bead removal solvent and adapted to apply edge bead removal solvent onto an edge bead formed on a wafer. The system also includes an absorbent material adapted to receive a droplet of edge bead removal solvent from the nozzle tip after the application of the edge bead removal solvent is completed.
Yet another aspect of the present invention relates to an edge bead removal system for applying an edge bead removal solvent on an edge bead formed on a wafer by a photoresist material application system. The system includes means for supplying an edge bead removal solvent, means for supplying air, and means for applying the edge bead removal solvent to an edge bead formed on a wafer. The means for applying the edge bead removal solvent includes a liquid supply path for moving the edge bead removal solvent from the means for supplying an edge bead removal solvent to the edge bead formed on the wafer and an air supply path for supplying a supply of air to the liquid chamber for removing an edge bead droplet formed on an end of the liquid supply path.
In yet another aspect of the invention an edge bead removal nozzle with a nozzle tip for applying an edge bead removal solvent on an edge bead formed on a wafer by a photoresist material application system is provided. The edge bead removal nozzle includes a liquid supply chamber adapted to be in fluid communication with a supply of edge bead removal solvent. The liquid supply chamber includes a first inner cylindrical surface made of a material that repels the solvent and a material that attracts the solvent.
Another aspect of the invention relates to a method for applying an edge bead removal solvent on an edge bead formed on a wafer by a photoresist material application system, and removing a droplet of edge bead removal solvent from a nozzle tip of an edge bead removal nozzle after applying the edge bead removal solvent. The method includes the step of providing an edge bead removal nozzle with a nozzle tip where the nozzle includes a liquid supply chamber adapted to be in fluid communication with a supply of edge bead removal solvent and an air supply chamber adapted to be in fluid communications with a supply of air. The edge bead removal nozzle has a first state for applying the edge bead removal solvent and a second state for removing the edge bead removal solvent from the nozzle tip. The air supply chamber is in fluid communication with the liquid supply chamber in the second state. The method further includes the steps of applying a supply of edge bead removal solvent to the edge bead formed on the wafer and providing a supply of air to the air supply chamber causing the removal of any remaining edge bead removal solvent from the nozzle tip of the nozzle.